Note: Descriptions are shown in the official language in which they were submitted.
10~:19~6
In the ar-t ol earth boring by percussive tool
means such as in rock drilling it has long,been common -
practice to direct a flow oE flushing fluid to the work ..
surface during ongoing drilling operations to flush detritus
from the bore hole and to cool the drill bit. For example, . ~.
many known rock drills have included axially aligned com-
municating bores in the hammer piston, striking element
and drill steel whereby a desirably simple and compact :
means has been provided for direc-ting a flow of flushing
fluid such as water to the bottom of the bore hole as well
as for such additional purposes as the disslpation of heat
generated within the drill. Although such flushing fluid
arrangements have generally served the~ purposes intended,
they have non~theless often been sub~ect to cert~i.n un-
des.irable de.E.ic:iencies. For exampLe, the flow of flush-
iny fluid throuyh the drill has not in all cases dissipated
heat generated within the drill casinu as effectively as
would be desirable. Furthermore, such arrangements have
commonly included a water tube extending within the axial- .: :
ly aligned bores in the hammer pis-ton and striking element
and having sealing means to protec-t internal drill portions
from damage due to the entry o:E water the~reinto during
operation. ~IeretoEore ther~ has been no ef:Eective back-
up sealing means -to pro-tect the drill interior from water ..
damage in the event of primary water tube seal failure.
According to the present invention, there is ;.
provided a fluid motor having a body r,lember and a piston
axially movable within the body member, the motor further ~ ~.
having motive fluid conducting means cooperable with a
source of motive fluid flow for conducting motive fluid
to the piston to drive the piston. An elonga-ted fluid :
conveying means extends wi-thin the body member and the
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piston, and a containment means is defined within the
motor and is adapted to contain therein a quantity of
heat transfer medium. The containment means includes :~
a pair of variable volume chambers and a passageway .
means communicating between the pair of variable volume
chambers. The passageway means has a passage portion
ex-tending within the piston such that the heat transfer :
medium contained in the passage portion is maintained
in heat exchange relation with the fluid conveying means.
The piston includes means effective to induce a flow
of such heat transfer medium within the passage portion
during the movement of the piston by increasing the
volume of on~ of the variable volume chambers while
d~cre~asincJ the volume o:E the other of the variable volume
chambers.
In a specific arrangement of the inven-tion,
the fluid conveying means includes an elongated tube
extending within a through bore formed in the piston.
I'he passage por-tion of the passageway may include a
peripheral clearance between the bore and the tube. ~he
chambers may be located adjacent spaced end por-tions
oE the piston. Thus, the volume oE each o:E the chambers
may be variable by the movement of the spaced end portions
into and out of the respective chamber adjacent thereto `~
during the movement of the piston. .
These features and advantages of the present
lnvention will become more readily apparent upon a reading :~
of the following description of the invention as shown
in the sole accompanying figure which illustrates in
side elevation and in partial longitudinal section a
rock drill cons-truc-ted in accordance with the principles
of the inven-tion described.
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There is generally indica-ted at 10 in the
figure a percussive rock drill powered by fluid motor
means which, it is to be understood from the outset,
comprises but one of numerous fluid motor configurations
adaptable for use in conjunction with the presen-t inven-
tion. The drill 10 is illustra-ted in simplified ~orm
solely for purposes ol clarity, and of course such
simplification is not intended to unduly limit the scope
of the invention described. Accordingly, as shown the
drill 10 comprises an elongated, generally annular body
member or rno-tor casing 14 disposed axially adjacent a
generally annular chuck housing 15. The casing 14 and
housing 15 are disposed axially intermediate a generally : :
disc-l.ike backhead 16 and a generally d.isc-li]ce ~ront
head 18 ancl rig:id:l.y sccured therebetweel- as by a plu.ral:ity
o:E lonyitucl:i.nally extending s.ide rods 20. ~s shown, rods
20 retain the casing 14 and housing 15 axially adjacent
from each other and axially intermediate the respective
~ront head and backhead 18, 16 by means of threaded end . .:
portins 24 thereof which pass through suitably aligned
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1~7~946
bores 22 in the Eront head and backhead and have cooper-
ably threaded nut members 26 engaged thereupon to fixedly
retain members 16, 14, 15 and 18 in the configuration
described and in forceful compressive engagement with each
other.
As noted hereinabove, the motor of drill 10 may
take the form of any of various well kno~ designs com-
prising generally a hammer piston element reciprocably
carried for controlled repetitive impacting upon a strik-
ing element. For purposes of illustrative simplicity the
drill herein is shown as having a motor of the so-called
"valveless distribution" type wherein a generally stepped
cylindrical hammer piston 28 is carried :Eor reciprocal
movement within an axial through bore portion 30 of a
generally elongated annular liner 32 fixedly disposed with-
in an axial through bore 34 in the casing 14 and substan-
tially axially coextensive therewith. As shown the piston
28 includes axially spaced apart rearward and ~orward
stem portions 28a, 28b, respectively, and an enlarged `~
int~rmediate portion 28c having lands as at 33 and adjac-
ent grooves 35 disposed for reciprocal movement within
an lntermediate,`generally stepped control portion 30a of
bore 30. Bore portion 30a communicates via suitable
pressure port means 36 and exhaust port means 38 with any
suitable pressure fluid system (not shown) such as a
hydraulic-fluid flow source whereby the reciprocal move-
ment of the piston 28 causes lands 33 and grooves 35 to
cyclically open and close the ports 36, 38 thus directing
motive fluid flow to sustain piston reciprocation in the
generally well known manner of valveless cycle fluid motors.
Inasmuch as such valveless motors are well known to those
versed in the art, furtheF detailed description thereof is
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~0~946
omitted herefrom. Suffice it to note in this regard that
in operation the self-sustained reciprocal movement of
piston 28 produces repetitive impacts of the forward
stem 28b upon a striking element shown as a striking bar
40 which is rotatably carried in any suitable manner
within housing 15 as by splined engagement at 42 within
an annular chuck gear 44 which is journaled in bearings
(not shown) for rotation within the housing 15. Any
suitably adapted rotation means such as a fluid rotation
motor 46 and cooperable gear train (not shown) carr:ied by
housing 15 may be utilized to drive the gear 44 and striking
bar 40 in rotation whereby a rotary impact dril].ing action
i9 generated. A forward end portion ~Oa of striking bar
40 extends forwardly of ~ront head 18 through an axial
through bore 50 in a front bushing member 52 and has a
drill steel 54 axially, rigidly affixed thereto as by a
known coupling sleeve 56. Drill steel 54 in turn has a
drill bit 48 rigidly affixed adjacent a forwardmost end
portion thereof whereby the rotary impact drilling action
of drill 10 is transmitted directly to bit 48 or
drilling into rock formations in the known manner.
The drill 10 includes means for delivering
flushing liquid such as water to the drill bit 48
comprised of an axial through bore 58 extending within
piston 28 and co~municating with an axially aligned
through bore 60 extending within the striking bar 40.
Bore 60 in turn communicates with an axial through bore
62 extending within the drill steel 54 whereby flushing
liquid may be directed to the bit 48 via a continuous
axially extending path comprised of the respective bores
58, 60 and 62.
1071946
To protec~ internal components of drill 10
from the entry of flushing water thereinto, the waterpass-
ing through bore 58 flows within a water tube 64 disposed
within the bore 58 and extending forwardly into bore 60.
The tube 64 also extends rearwardly in~o a generally
stepped, axial through bore 66 extending within backhead
16.
The tube 64 is provided with sealing means
adjacent opposed longitudinal end portions thereof within
bores 66 and 60 whereby the motor components contained
within casing 14 are completely isolated from flushing
water passed through the tube 64. The rearward sealing
means is shown as comprising a suitably resilient
annular seal 68 surrounding tube 64 within an enlarged
portlon 66a of bore 66 and axially intermediate a radially
inwardly extending shoulder 70 which defines the forward
end of bore portion 66a, and a radially outwardly flared
end portion 72 of tube 64. A water tube clamping membe~
74 is threadingly engaged within a rearwardmost threaded
end`portion 66b of bore 66 whereby a forward end 74a o~
the member 74 forcefully engages flared end 72 to cap-tive-
ly retain seal 68 intermediate shoulder 70 and the end
portion 72 to effectively seal the annular space radially
interemdiate tube 64 and bore 66.
Adjacent the forward end of tube 64 within bore
60 a suitable seal such as resilient wiping seal 76 is
provided in a form of an annulus sealingly seated within
an annular groove 78 spaced forwardly from the rearward-
most end of bore 60. Seal 76 surrounds the tube 64 and
extends in sealing engagement radially intermediate the
tubo 64 and groove 78.
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10~946
I~ will be understood that flushing water may
be introduced into the rearwardmost end of ~ube 64 in any
conventional manner as through an inlet port 80 communica-
ting with any suitable water pressure source (not shown)
and further communicating via open passages 82 formed
in backhead 16 with an enlarged annular bore portion 66c.
Bore portion 66c, in turn, communicates via suitable
formed transverse passages 84 and a.forwardly extending
axi.al passage 86 in member 74 with the tube 64 whereby in
practice the ~lushing water is directed under pressure
through tube 64 and thence to the drill bit 48.
To protect the drill components within casing l4 :
from water damage in the event of water tube seal failure,
there is provided by the instant invention a fluid pressure
sealing means wherein a pressurized charge of gas, air for
example, is employed to back up the water tube seals as
follows.
Within bore 30 in which piston 28 reciprocates
there are formed chambers 88 and 90 adjacent opposed
longitudinal ends thereof to receive respective piston . .
stems 28a, 28b, during the reciprocal travel of the p:iston
28 in operation. The chamber 88, shown as being Eormed :
wlthin a rearward enlarged end portion 30d oE bore 30
and an adjacent enlarged forward end portion 66d of bore : .
66, is sealed against fluid leakage therefrom by means .. ..
of the previously described rearward water tube seal 68 :
and additionally by such suitable sealing means as a ~.~ .... ..
me.tallic face seal formed intermediate adjacent surfaces :
of backhead 16 and liner 32 as at 92 radially outwardly
adjacent the chamber 88, and an annular wiping seal 94 .
disposed within an annular groove portion 96 of bore 30 l
forwardly of chamber 88 and surrounding piston stem 28a .
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~1946
in sealing engagement therewith. Accordingly, the
chamber 88 is sealed against the escape of gas therefrom
by any path except through an annular clearance 98 which
is provided intermediate the exterior wal]. of tube 64
and the bore 58 and extends longitudinally to communicate
intermediate chambers 88 and 90.
Chamber 9V is formed in a manner similar to
chamber 88, being formed within a forward end portion 30e
of bore 30, and within forwardly adjacent internal peri-
pheral portions of the chuck gear 44 as a-t 100 radially
intermediate the striking bar 40 and the internal periphery
o~ gear 44. As shown, the chamber 90 may additionally
comprise spaces axially intermediate bore portion 30e and
space 100 as ~or e~ample space 102 extending a~ially inter-
mediate the forward ends o~ casing 14 and liner 32, and
the adjacent rearward end of gear 44, of further portions
o~ the voidsj within the interior periphery o~ gear 44 as
at 104 adjacent a forward end portion thereo~. It is to
be understood that the components normally disposed within
the gear 4b~ such as striking bar 40 and a rear bushing 41
for example, do not provide a sealing fit therewithin and
clearances are thus maintained which provide for relative-
ly free flow of gas throughout the entire chamber 90
intermediate the a~ial ends of the gear 44.
The chamber 90 is sealed against the escape of
gas therefrom by the previously described forward water
tube seal 76 and by additional seals shown as including:
an annular piston stem wiping seal 1~6 similar in all
respects to the previously described seal 94; an
annular wiping seal 108 interposed radially intermediate
relatively rotating portions of gear 44 and casing l~
adjacent a rearward end o~ gear 44; an entirely similar
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wiping seal 110 disposed radially intermediate a forward
end portion of gear 44 and housing 15; an annular seal
112 disposed radially intermediate liner 32 and caslng
14 adjacent a forward end portion thereof; and an annular
wiping seal 120 disposed radially intermediate striking
bar 40 and chuck housing 52 within bore 50.
It will be seen that by means of -the sealing
arrangements provided> chambers 88 and 90 are completely
sealed against the exit o~ gas therefrom except that gas -~
may flow between chambers 88 and 90 via clearance 98 ex-
tending therebetween within piston 28. Thus, a charge
of pressurized gas may be maintained therewithin to pro-
vide improved sealing according to one Eeature of the
ins~an~ invention. In order to introduce such gas into
the chambers 88 and 90 there may be provided gas inlet
means sho~l as inlet passage 113 formed within backhead
16 and communicating with chamber 88, and having a gas
~ine connection 11~ whereby an external source of pressur-
ized gas may be applied to introduce air or other gas
into the chambers 88, 90 via passage 113. The connection
~ is shown as being sealingly closed by a cap 116 to
preclude escape of contained gas to the atmosphere.
The gas introduced into the chambers 88 and 90
preferably is under positive pressure somewhat higher
than the flushing water pressure whereby the large and
undesirable extruding forces of the flushing water upon
the water tube seals 68, 76 are effectively cancelled
by the opposed gas pressure. In addition, the pressure
differential by which the pressure of the gas within
chambers 88, 90 exceeeds the flushing water pressure
provides a small net outward pressure at all times across
the respective water tube seals 76, 68 such that a failure
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10719~6
of one or both o these seals will result in a flow of ,-
gas outwardly from chambers 88, 90 thereby precluding '
any entry of flushing water thereinto.
According to an additional feature of the
instant invention, as piston 28 reciprocates in operation
and the stems 28a,and 28b alternately move into and out
of the respective chambers 88 and 90~ some of the gas
contained within the respective chambers 88,90 i5 cyclic-
ally pumped therebetween through the clearance 98, the - ,
chamber 88 being partially emptied of gas and the chamber
90 being filled on piston upstroke, and the chamber 90
being partially emptied and chamber 88 being filled on
the piston downstroke. This'pumping of gas between '
chambers 88 and 90 improves heat dissipation from the
drill 10 and ensures uniform temperature of the piston
28 inasmuch as hea~ transfer from the piston 28 to the
flowing gas occurs uniformly along the length thereof as
the gas flows through passage 98 intermediate chambers ;'
88, 90. The heat is thence uniformLy conducted from the
flowing gas to the flushing water through the wall o tube
, 64 along substantially the entire length thereof. Further-
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more, by suitable sizing of chambers 88, 90 and clearance
98 the described cyclic p~lmping of gas may be made to
create turbulent gas flow which further enhances heat
transfer from the drill 10 to the flowing water. Such
turbulent gas flow decreases the thermal insulating ''
capability of the flowing gas as by breaking up the
' boundary gas layer adjacent the periphery of bore 60 and
tube 64. ' '
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Of course it will be appreciated that ~he
communicating passage 98 between chambers 88 and 90 need
not take a form of a clearance around water tube 64. For
example, the described heat transfer advantages may be .
provided for by a separate passage or plurality of
passages extending within piston 28 and communicating .
with tube 64 in lie~ of or in addition to the clearance
98. Additionally, it should be appreciated that the
described heat dissipation of gas pumping is operable
with any number of gases over a wide range o~ gas pressures :
including air at atmospheric pressure.
According to the foregoing description, there is .:
provided novelmeans or dissipating heat from interior
portions af a percussi~e rock drill and means for guarding
against the en~ry of ~lushing liquid therein-to in the event
of a seal ~ailure along the flushing liquid path there-
through. Notwithstanding the reference herein to a specific
preferred embodiment of the invention, it is of course to .
be appreciated that the invention being broadly conceived
is subject to various modi~ications of the described embodi- .
ment. For example, the form of piston 28 may be varied
withi~l a wide design latitude, chambers 88 and 90 ma~
be independentl~ pressurized and need have no commun-lcation
therebetween for purposes of the described water tube
sealing feature, chambers 88 and 90 may be adapted to
communicate continuously with a reservoir of gas pressure,
chambers 88, 90 might be supplemented by additional variable
volume chambers and additional passageway means communi-
cating between such additlonal chambers and chambers 88,
90, the striking element might be an anvil bloc~ in lieu
of striking bar 40 and need not necessarily be rotatably
carried, and the like. These and other embodiments and ~
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l~ql9~6
modifications having been envisioned and anticipated by
the inventor it is respectfully reques-ted that the inven-
tion be interpreted broadly and limited only by ~he scope
of the claims appended hereto.
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